Computer system speeds continue to increase and more computer systems are connected to communicate with other computer systems daily. As the volume of digital data communicated between computer systems increases, there is a need to develop higher bandwidth communication links. Often, these communication links are part of a network, such as a local area network (LAN), metro area network (MAN), or a wide area network (WAN).
A network includes network nodes that provide network related functions. Each network node is a grouping of one or more network elements, such as computer systems, and each network node includes one or more communication links connected to the network. In addition, each network node is administered as a single entity. Network elements in a network node can be at one or more sites and a single site may contain more than one network node. Network elements on a network communicate with other network elements on the network by employing some type of suitable network communication, such as synchronous communication and/or asynchronous communication.
In synchronous communication, transmission system payloads are synchronized to a master clock that is traceable back to a highly stable reference clock. The digital transitions in signals occur at essentially the same rate. Synchronous communication often uses time division multiplexing (TDM) as a mechanism for dividing the bandwidth of a communication link into separate channels or time slots. In TDM, multiple data streams are put into a single signal by separating the signal into many segments, each having a very short duration. Each individual data stream is reassembled at the receiving end based on the timing. A synchronous TDM interface transmits and receives data traffic at a constant bit rate, whether or not data is available for transmission.
One type of synchronous network is a synchronous optical network and synchronous digital hierarchy (SONET/SDH) ring network. SONET and SDH are a set of related standards for synchronous data transmission over fiber optic networks. SONET is the United States standard published by the American National Standards Institute (ANSI) and SDH is the international standard published by the International Telecommunication Union (ITU). A SONET/SDH ring network is one medium of choice for delivering services over a MAN and/or a WAN.
In asynchronous communication, transmission system payloads are not synchronized to a master clock. Instead, each network element operates from its own clock. Data packets or frames are transmitted asynchronously as the packets become available for transmission. In the case where there are no packets available for transmission, the asynchronous interface can remain inactive.
In some networks, network elements on the network communicate with other network elements on the network through synchronous TDM and asynchronous packet interfaces. Data traffic crosses one or more synchronous TDM interfaces and one or more asynchronous packet interfaces as it travels from one network element to another network element on the network. Data packets are transmitted by the asynchronous packet interfaces as they become available and data traffic is transmitted at a constant bit rate by the synchronous TDM interfaces. This can lead to serious problems in maintaining data transmission rates on the synchronous TDM networks. To maintain constant bit rates through the synchronous TDM interfaces, large buffers are employed to avoid overflow and underflow conditions. Implementing large buffers in a system and/or in an integrated circuit chip uses space and adds cost to the system and/or chip. In addition, the feedback status of the buffers becomes a time critical event to avoid overflow and underflow conditions.
For these and other reasons there is a need for the present invention.